1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine, a laser beam printer, a facsimile, a plotter, or the like, a control method thereof, a program and a recording medium, particularly to an image forming apparatus wherein according to a detection result of a toner adhesion amount in toner adhesion patterns, a process control or a toner density control is performed.
2. Description of the Related Art
In an image forming apparatus of an electrophotographic type such as a copying machine, a printer, a facsimile, or the like, an image carrier including a photoreceptor is uniformly charged by a charger. A latent image is formed by an exposure device. Then, the latent image is developed by a developing unit, to be transferred by a transfer device to a transfer paper.
In the electrophotographic image forming apparatus of this kind, there is conventionally used a toner density control system, wherein toner adhesion patterns are formed in a non-image area of the image carrier, a density of the toner adhesion patterns is detected and measured by a photosensor of an optical reflection type and according to the detection results, toner supply from a toner supply device to the developing unit is controlled.
In the toner concentration control system, of output values of the optical reflection type-photosensor, for example, if an output value of the optical reflection type-photosensor corresponding to the toner adhesion patterns on the image carrier is represented by Vsp and an output value of the optical reflection type-photosensor corresponding to a toner non-adhesion part on the image carrier is represented by Vsg, generally, a toner supply control is performed so that Vsp/Vsg becomes a constant. When an amount of toner adhesion of the toner adhesion patterns decreases, Vsp/Vsg increases and a toner density of a developer in the developing unit is determined as low. Thereafter, the toner is supplied from the toner supply device to the developing unit. Conversely, when Vsp/Vsg is low, since the toner concentration of the developer in the developing unit is determined as high, the toner is not supplied. Thus, the concentration of the toner in the developing unit remains unchanged.
For example, as disclosed in Japanese Patent Application Publication Number 2006-251406, a toner density of a developer in a developing unit is detected. In accordance with Japanese Patent Application Publication Number 2006-251406, an image forming apparatus is configured to include a plurality of image carriers; a toner image forming device, whereby toner images in a plurality of colors are formed with toners of mutually different colors, on the plurality of image carriers, respectively; a transfer member to transfer the toner images, formed respectively on the plurality of image carriers, either to a surface of a transfer member moving a plurality of transfer positions facing the plurality of the image carriers respectively, or to a recording material carried on the surface of the transfer member; a plurality of toner image density detecting devices to detect respectively a toner adhesion amount, of toner patterns formed on the image carriers respectively and transferred on the transfer member, in a plurality of colors for image adjustment; and a controlling device which performs at least one of a process control to change an image forming condition, and a toner concentration control to change a toner supply amount, based on detection results of the toner adhesion amount of the toner adhesion patterns in the plurality of colors.
The plurality of image carriers are arranged to be aligned in a moving direction of the surface of the transfer member. The plurality of image density detecting devices are arranged in a direction intersecting the moving direction of the surface of the transfer member. The image forming apparatus further includes an apparatus state recognition device to recognize at least one of a use state and a use history of an apparatus main body. In accordance with the recognition result of the apparatus state, an array of the toner adhesion patterns in the plurality of colors, which is transferred and formed on the transfer member, is switched.
Furthermore, the image forming apparatus is configured in which an order of an image formation timing of the toner adhesion patterns in the plurality of colors is changed in accordance with the array of the toner adhesion patterns. As illustrated above, in accordance with the recognition result of the apparatus state, the array of the toner adhesion patterns in the plurality of colors, which is transferred and formed on the transfer member, is switched. Thus, according to the recognition result of the apparatus state, the optimum toner adhesion patterns can be generated and the image density thereof can be detected. Therefore, corresponding to the apparatus state of the image forming apparatus, the optimum toner adhesion patterns can be formed, and an image forming control can be performed.
In Japanese Patent Number 3219882, a process controlling device of an electrophotographic apparatus is disclosed, wherein a toner image density detecting device is provided to optically detect a density of a referential toner image generated on a photoreceptor. Based on detection results of the toner image density detecting device, respective parts of an electrophotographic process are controlled and a quality of an image formed is stabilized. In the process controlling device of the electrophotographic apparatus, an information processing device is provided to control the respective parts of the electrophotographic process, based on detection results obtained by the toner image density detecting device, after the referential toner image is formed between plural toner images for copying. To control the respective parts of the electrophotographic process, the above-mentioned information processing device gradually and sequentially alters control values of the respective parts of the process when the control values exceed predetermined values, so as to prevent a drastic change in image quality generated in the case of performing consecutive copying. In the process controlling device of the electrophotographic apparatus, deterioration in operation efficiency can be avoided because the process control is performed during intervals wherein the respective toner images are generated to form the image. In addition, since control data obtained from the referential toner image is immediately utilized to form a toner image for copying, the accuracy of the process control is enhanced. Furthermore, to control the respective parts of the electrophotographic process, since the information processing device is configured to perform the control gradually, drastic change in the image quality in the case of forming a plurality of images can be prevented. Thus, incongruous use of a copying machine by a user can be alleviated.
Meanwhile, due to a sensitivity deterioration of the photoreceptor with the lapse of time, or a sensitivity fluctuation of the photoreceptor resulting from an environment wherein the main body of the copying machine is used, or the like, under constant image forming conditions such as electrifying, exposure, developing, or the like, the image quality is unstable. Therefore, conventionally, a surface potential of the photoreceptor is detected by a potential sensor, etc., whereby the above-mentioned image forming conditions are controlled based on the detection results, so as to stabilize the image quality.
For example, in Japanese Patent Application Publication Number 2003-84513, an image forming apparatus is disclosed, which includes a toner cartridge attachable thereto and detachable therefrom; an electrifying device to apply an electrifying voltage to a photoreceptor drum; a developing voltage applying device to apply a developing voltage to a developing roller; and an image adjusting process control device. The toner cartridge includes a nonvolatile memory to record the printed sheets, a photoreceptor drum, a toner storage section, and a developing roller, which are integrally configured; a surface potential sensor to detect a surface potential of the photoreceptor drum; a toner concentration sensor to detect a toner concentration of detection patterns formed on the photoreceptor drum; and a toner end sensor to detect a toner amount in the above-mentioned cartridge. The image adjusting process control device adjusts an electrification output setting and a developing output setting, so that the surface potential detected by the surface potential sensor and the toner concentration detected by the toner concentration sensor reach prescribed values, in order to optimize an image output. The image adjusting process mode is performed by the image adjusting process control device whenever the number of printed sheets reaches a prescribed value, and the adjusted output value is recorded in the nonvolatile memory on the toner cartridge. In Japanese Patent Application Publication Number 2003-84513, it is also disclosed that both the number of printed sheets, as well as the electrifying output set value and the developing output set value are recorded in the above-mentioned nonvolatile memory, and that the image adjusting process control device selects a period to execute the image adjusting process mode, based on a variance between the output value and an estimated value. However, being comparatively expensive, the potential sensor is virtually only included in a top-of-the line image forming apparatus.
Meanwhile, in Japanese Patent Number 3219882, as illustrated above, the process controlling device of an electrophotographic apparatus is also disclosed, wherein the toner image density detecting device is provided to optically detect the density of the referential toner image generated on the photoreceptor. Based on detection results of the toner image density detecting device, respective parts of the electrophotographic process are controlled and the quality of the image formed is stabilized. In the process controlling device of the electrophotographic apparatus, there are also provided an internal temperature detecting device, to detect a temperature inside the electrophotographic apparatus; as well as a frequency control device to control a frequency at which the respective parts of the electrophotographic process are controlled, when a temperature, detected by the internal temperature detecting device, differs from a temperature detected, at which the respective parts of the electrophotographic process are controlled last time, by a predetermined value, in order to control the respective parts of the electrophotographic process once again. Thus, the process control is performed corresponding to a temperature variation in the electrophotographic apparatus. Accordingly, on the one hand, the process can be controlled less frequently; on the other hand, drastic change in the image quality can be prevented. Therefore, for one thing, an undesirable increase in toner consumption can be prevented; and for another, the accuracy of the process control can be enhanced, whereby the optimization of the image forming can be achieved.
To summarize, as illustrated above, the process control can be variably or flexibly performed corresponding to the state of the image forming apparatus. However, when focusing on varying parameters of gradation patterns, few reference documents can be referred to other than Japanese Patent Application Publication Number 2006-251406. Conventionally, although an image forming apparatus with a small gradation number used for the process control is commercially available, the gradation number is invariable, namely, the gradation number cannot be varied corresponding to the state of the apparatus. When the gradation number is small and invariable, even a development characteristic differs greatly from a typical one, a measurement of the development characteristic cannot be performed appropriately. Consequently, the process control may not be performed successfully.